The rapid, robust recording of three-dimensional images is becoming increasingly important in many fields, particularly in sensor technology. Because of the measurement basis required for the trigonometric calculation of a distance value, known triangulation methods are only suitable for distances of up to about 2 m and are of limited application. There is a great variety of applications for cost-effective three-dimensional (3D) measurement systems for recording and evaluating, particularly for measuring larger areas of—for example—from 20 cm up to 50 m, for example in the fields of automotive engineering, navigation, building systems, security and alarm systems, or automation engineering. At present, the measurement of larger 3D scenes and 3D objects can only be done statically by means of photogrammetry or by scanning with a 3D laser radar, with correspondingly high expenditure in terms of cost and time.
In German patent application no. 198 33 207, a method is described in which the extremely short integration time of a CMOS photosensor, which is—for example—30 ns, is used in combination with a likewise short laser pulse, in order to generate distance-measuring images quickly and economically by evaluating light propagation time measurements. Concurrently with the emission of the laser pulse, a measurement window is opened on the CMOS image sensor via a trigger and the light intensity of the laser pulse is detected following reflection on the object to be measured in two consecutive measurements with the integration times T1 and T2. The propagation time T0, and thus the distance to the object point, is precisely calculated by measuring the integrated intensity U1 and U2 within two measurement windows with integration times T1 and T2, according to the arithmetic formula:
  d  =            1      2        ⁢    c    ⁢                                        U            2                    ⁢                      T            1                          -                              U            1                    ⁢                      T            2                                                U          2                -                  U          1                    
A laser light source is used as the illumination. It is synchronized with the start of the integration time T1 and T2 and has short rise times (approx. 1 ns) and an output power which is as constant as possible.
However, because of the difference and quotient formation, the application of this formula requires a measurement to be carried out with light intensities whose integrated photoelectric voltages must be significantly higher than the upper noise limit of the CMOS image sensor. Even though it is possible for the results of numerous laser pulse illuminations to be added together, any improvement in the signal/noise ratio can only be achieved using the root of the laser pulse count. Furthermore, final rising edges of the laser pulse and inevitable non-linearities in the integration behavior of the CMOS image sensor result in measurement errors that require additional calibration procedures.